MR imaging is a medical imaging technique that uses an applied static magnetic field (B0) and radio frequency (RF) pulses to generate images (e.g., via slices) of organs and structures inside the body. During MR imaging, the static magnetic field causes magnetic moment vectors of protons (typically in hydrogen atoms of water molecules) to align with the static magnetic field. The RF pulses cause the magnetic moment vectors of the protons to be displaced (e.g., rotate) relative to the magnetic field and re-align with the magnetic field. A MR imaging scanner picks up magnetic signals from the protons in the body that result from magnetization moment vectors re-aligning with and rotating around the static magnetic field. The signals may then be converted into images based on the location and strength of the incoming signals.
MR imaging uses sequences of the RF pulses and the magnetic gradient fields to spatially encode the MR signal of a signal carrier such as tissue in a patient. An MR imaging sequence may be separated in sections that are associated with three orthogonal spatial dimensions. A slice selection direction defines a two dimensional plane or slice of excitation. The phase encoding and readout (frequency) encoding direction define the remaining two directions of the plane.
Conventional sequence design methods and systems use dedicated timing of gradient pulses and tissue dependent physiological parameters as contrast parameters. For example, tissue specific parameters serving as contrast parameters include longitudinal or transversal relaxation parameters (T1, T2), blood flow, diffusion or even oxygenation level of blood. The corresponding sequences may exhibit sophisticated and carefully adjusted timing of RF and gradient pulses. Although MR imaging sequence design methods and systems exist, there is a continuing need for more and different sequence design methods and systems.